I've seen Renaissance examples of combo weapons, even one of a dagger that shot the tip of the knife as a projectile... also seen guns hidden in covert items these days (cellphones was the newsmaker in the UK a while back, with people making .22 zip guns in cellphones), but you don't see as many combo melee/firearm weapons these days.

Here's an interesting demo of one:http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=29251810